Written with clarity, directness, and humour, The Sexual Brain examines the biological roots of human sexual behavior. It puts forward the compelling case that the diversity of human sexual feelings and behavior can best be understood in terms of the development, structure, and function of the brain circuits that produce them. A new afterword to this paperback edition takes up the work of Dean Hamer and his colleagues, who in 1993 produced molecular genetic evidence of a gene that influences sexual orientation in men.